Grinding wheel and method of manufacturing grinding wheel

ABSTRACT

Object: To provide a grinding wheel and a method of manufacturing a grinding wheel having added value while providing a suppressed manufacturing cost. Solution Means: The grinding wheel is a grinding wheel including an abrasive portion including nonwoven fabric, wherein the abrasive portion includes an outer peripheral portion formed with the nonwoven fabric including abrasive grains on an outer peripheral side, and an inner peripheral portion formed with the nonwoven fabric not including the abrasive grains, and a ratio of a thickness in a radial direction of the outer peripheral portion to a thickness in a radial direction of the abrasive portion is from 3% to 60%.

TECHNICAL FIELD

One aspect of the present disclosure relates to a grinding wheel and amethod of manufacturing a grinding wheel.

BACKGROUND ART

In the related art, as a grinding wheel, there is one described inPatent Document 1. The grinding wheel includes a core member and anabrasive portion provided around an outer periphery of the core memberand including nonwoven fabric. The abrasive portion is formed with thenonwoven fabric including abrasive grains.

CITATION LIST Patent Documents

Patent Document 1: JP 2007-290061 A

SUMMARY OF INVENTION Technical Problem

Here, the grinding wheel described above has a problem of a large amountof the abrasive grains incorporated in the abrasive portion and a highmanufacturing cost. Therefore, there has been a demand for suppressingthe manufacturing cost of the grinding wheel.

Solution to Problem

A grinding wheel according to an aspect of the present disclosure is agrinding wheel including an abrasive portion including nonwoven fabric,wherein the abrasive portion includes an outer peripheral portion formedwith the nonwoven fabric including abrasive grains on an outerperipheral side, and an inner peripheral portion formed with thenonwoven fabric not including the abrasive grains, and a ratio of athickness in a radial direction of the outer peripheral portion to athickness in a radial direction of the abrasive portion is from 3% to60%.

A grinding wheel according to an aspect of the present disclosure is agrinding wheel including an abrasive portion including nonwoven fabric,wherein the abrasive portion includes an outer peripheral portion formedon an outer peripheral side, and an inner peripheral portion softer thanthe outer peripheral portion, and a ratio of a thickness in a radialdirection of the outer peripheral portion to a thickness in a radialdirection of the abrasive portion is from 3% to 60%.

A method of manufacturing a grinding wheel according to an aspect of thepresent disclosure is a method of manufacturing a grinding wheelincluding an abrasive portion constituted by laminating a plurality ofnonwoven fabric sheets, the method including the steps of: laminating aplurality of nonwoven fabric sheets in a circumferential direction,forming a gap between the nonwoven fabric sheets adjacent to each otherin the circumferential direction, and incorporating abrasive grains inan outer peripheral edge portion of each of the nonwoven fabric sheetsbetween which the gap is formed.

Advantageous Effects of Invention

According to an aspect of the present disclosure, a grinding wheel and amethod of manufacturing a grinding wheel having added value whileproviding a suppressed manufacturing cost can be provided.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view of a grinding wheel according to a firstembodiment of the present disclosure.

FIG. 2 is a plan view of the grinding wheel illustrated in FIG. 1.

FIGS. 3A and 3B are enlarged views of the outer peripheral portion andthe inner peripheral portion.

FIGS. 4A and 4B are enlarged views illustrating layer configurations ofan abrasive portion.

FIG. 5 is a view illustrating a method of manufacturing the grindingwheel according to the first embodiment of the present disclosure.

FIG. 6 is an enlarged view illustrating a state in which abrasive grainsare applied to an outer peripheral portion.

FIGS. 7A to 7C are views for explaining an action and an effect of thegrinding wheel according to the first embodiment of the presentdisclosure.

FIGS. 8A to 8E are views for explaining a grinding wheel according to amodification and a method of manufacturing the same.

FIG. 9 is a graph showing measurement results of grinding wheelsaccording to examples and a comparative example.

FIG. 10 is a plan view of a grinding wheel according to a secondembodiment of the present disclosure.

DESCRIPTION OF EMBODIMENTS

Detailed descriptions of the embodiments according to the presentinvention will be given below with reference to the attached drawings.In the description of the drawings, identical or equivalent elements aredenoted by the same reference signs, and redundant description of suchelements will be omitted.

First Embodiment

FIG. 1 is a perspective view of a grinding wheel 1 according to a firstembodiment of the present disclosure. FIG. 2 is a plan view of thegrinding wheel 1 illustrated in FIG. 1. According to the grinding wheel1 according to the first embodiment, the following problems can besolved while a manufacturing cost is suppressed. That is, roughness of apolished surface of an object polished by using a conventional grindingwheel has been dependent on a material of the grinding wheel (nonwovenfabric, abrasive grains incorporated in nonwoven fabric, an adhesive,and the like). Accordingly, in the case of performing polishing at aplurality of stages of roughness (for example, the case of performingfine finish after performing rough finish), preparation of a pluralityof grinding wheels has been required. Therefore, labor and man-hours forreplacing the grinding wheels and the like have been required. Withrespect to such a problem, the grinding wheel 1 can stably apply aplurality of stages of abrasive force to a surface to be polished of anobject.

The grinding wheel 1 is a member for polishing a surface to be polishedBF (see FIG. 2) of an object W with an outer circumferential surface 2a. The grinding wheel 1 is a cylindrical member with a central axis CLas a reference. As illustrated in FIGS. 1 and 2, the grinding wheel 1includes an abrasive portion 2 and a core member 3. Note that in thefollowing description, a direction in which the central axis CL extendsis referred to as an “axial direction.” A direction orthogonal to thecentral axis CL is referred to as a “radial direction.” A directionaround the central axis CL is referred to as a “circumferentialdirection.”

The core member 3 is a member provided at a center position of thegrinding wheel 1. The core member 3 is a cylindrical member with thecentral axis CL as a reference. The core member 3 is a portion throughwhich a shaft AX (see FIG. 2) is inserted for rotating the grindingwheel 1. The core member 3 is constituted with, for example, a materialhaving rigidity such as a resin and a metal.

The abrasive portion 2 is provided in an outer periphery of the coremember 3, and is a member including nonwoven fabric. The surface to bepolished BF is polished by rotating the outer circumferential surface 2a of the abrasive portion 2 in a state where the outer circumferentialsurface 2 a is in surface contact with the surface to be polished BF ofthe object W. The abrasive portion 2 includes an inner peripheralportion 2A formed on the inner peripheral side and an outer peripheralportion 2B formed on the outer peripheral side. The outer peripheralportion 2B is formed having a predetermined thickness in the radialdirection from the outer circumferential surface 2 a. The outerperipheral portion 2B is formed to surround the inner peripheral portion2A across the entire region in the circumferential direction and theaxial direction.

As illustrated in FIG. 3A, the outer peripheral portion 2B is formedwith nonwoven fabric 11 including abrasive grains 12. The abrasivegrains 12 are held in fibers of the nonwoven fabric 11 via an adhesive13. Note that the adhesive 13 also functions to bond the fibers of thenonwoven fabric 11 together. According to such a configuration, when theouter peripheral portion 2B comes into contact with the surface to bepolished BF of the object W (see FIG. 2), the surface to be polished BFcan be polished with the abrasive grains 12. As illustrated in FIG. 3B,the inner peripheral portion 2A is formed with the nonwoven fabric 11not including the abrasive grains 12. The abrasive grains 12 are notattached to the nonwoven fabric 11 of the inner peripheral portion 2A.Note that the inner peripheral portion 2A may include the adhesive 13 tobond fibers of the nonwoven fabric 11 together. Note that the innerperipheral portion 2A may include no abrasive grains 12, but when theinner peripheral portion 2A has a cushioning function as describedbelow, the inner peripheral portion 2A may include a slight amount ofthe abrasive grains 12.

As the nonwoven fabric used in the abrasive portion 2, nonwoven fabricincluding polyamide (for example, nylon 6 and nylon 6,6 includingpolycaprolactam or polyhexamethyl adipamide), a polyolefin (for example,polypropylene and polyethylene), a polyester (for example, polyethyleneterephthalate), and a thermoplastic organic fiber such as polycarbonatemay be used. Nonwoven fabric including nylon and polyester fibers arecommonly used.

The thickness of the fiber is generally approximately from 19 to 250 μm.Intersecting, contacting points of the arranged fibers are bonded toeach other by friction force, adhesive force, and the like. Bondingbetween the fibers may be made by using the adhesive 13 as describedabove, but may be made by the fibers themselves being melted.

The abrasive grains 12 include any known abrasive material, and acombination and an agglomerate of such materials. Examples of a softabrasive material include, but are not limited to, an inorganic materialsuch as flint, silica, pumice, and calcium carbonate, and an organicpolymer material such as polyester, polyvinyl chloride, methacrylate,methyl methacrylate, polycarbonate, and polystyrene, and a combinationof any of the above-described materials. Examples of a hard abrasivematerial include, but are not limited to, aluminum oxide such asaluminum oxide, heat-treated aluminum oxide, and white aluminum oxide,and silicon carbide, alumina zirconia, diamond, ceria, cubic boronnitride, garnet, and a combination thereof.

As the adhesive 13, a thermoset adhesive such as an aqueous suspensionand an organic solvent solution of epoxy, melamine, phenol, isocyanateand isocyanurate resins, or a rubber-based polymer solution orsuspension of SBR, SBS, SIS, and the like can also be used. These areapplied to fibers by an immersion coating method, a roll coating method,a spray coating method, and the like, and cured to form nonwoven fabric.The adhesive 13 that bonds the fibers of the nonwoven fabric togethermay be different from or the same as the adhesive 13 that bonds thefibers of the nonwoven fabric 11 and the abrasive grains 12. When thesame adhesive 13 is used, the bonding between the fibers of the nonwovenfabric 11 and the bonding between the fibers of the nonwoven fabric 11and the abrasive grains 12 may be performed simultaneously.

Next, relationship between the inner peripheral portion 2A and the outerperipheral portion 2B will be described in further detail with referenceto FIGS. 2, 4A and 4B. As described above, the inner peripheral portion2A includes no abrasive grains 12 in the nonwoven fabric 11, and theouter peripheral portion 2B includes the abrasive grains 12 in thenonwoven fabric 11. Accordingly, the abrasive portion 2 includes theouter peripheral portion 2B that is hard and formed on the outerperipheral side, and the inner peripheral portion 2A that is softer thanthe outer peripheral portion 2B. Thus, the abrasive portion 2 includesthe inner peripheral portion 2A that functions as a cushion member at aposition on the inner peripheral side than the outer peripheral portion2B with which polishing is performed. Accordingly, as illustrated by animaginary line in FIG. 2, when the outer circumferential surface 2 a ofthe abrasive portion 2 is relatively subjected to force F from the outerside in the radial direction, the inner peripheral portion 2A easilydeforms, and thus the outer circumferential surface 2 a easily deformstoward the inner peripheral side.

A radius (R0) of the outer circumferential surface 2 a of the abrasiveportion 2 is not particularly limited, but is set to approximately from10 to 600 mm or from 20 to 300 mm, for example. A radius of an outercircumferential surface of the core member 3 is not particularlylimited, but is set to be in the range approximately from 2 to 400 mm orfrom 3 to 200 mm, for example. The size (width) in the axial directionof the abrasive portion 2 is not particularly limited, but is set to bein the range approximately from 5 to 3000 mm or from 10 to 1500 mm, forexample.

The thickness in the radial direction of the abrasive portion 2 isreferred to as a “thickness R1,” and the thickness in the radialdirection of the outer peripheral portion 2B is referred to as a“thickness R2.” At this time, a ratio of the thickness R2 of the outerperipheral portion 2B to the thickness R1 of the abrasive portion 2(=R2×100/R1) may be set to 3% or more, and may preferably be set to 5%or more, and may be set to 10% or more. Thus, it is possible to suppressthe occurrence of early wear, cracking, and the like of the outerperipheral portion 2B due to the outer peripheral portion 2B being toothin. In addition, maximum abrasive force of the abrasive portion 2 canbe increased. Here, as indicated by “MG” in FIG. 7A, the maximumabrasive force refers to abrasive force by which roughness of the objectW becomes substantially constant, regardless of increased pressing ofthe abrasive portion 2 against the object W. The maximum abrasive forceis substantially equal to maximum abrasive force of an abrasive portionincluding the abrasive grains 12 in the entire region in the radialdirection (maximum abrasive force of a graph G2 in FIG. 7A). When R2 x100/R1 is within a predetermined range, a graph will have multiplestages as in a graph G1 in FIG. 7A (two stages in the case of the graphG1). That is, in addition to a region of the maximum abrasive force, aregion in which there is little change in roughness due to increasedpressing (the region may be referred to as first stage abrasive force)appears. That is, a plurality of stages of roughness or amounts ofabrasion can be achieved with a single wheel. In addition, the ratio maybe set to 60% or less, or may be set to 50% or less, or may be set to40% or less. Accordingly, it is possible to suppress difficulty inadjustment of roughness due to the outer peripheral portion 2B becomingtoo thick and the abrasive portion 2 becoming difficult to deform.

The maximum abrasive force varies depending on an object or application.Abrasive force is expressed by an amount of abrasion and roughness. Theamount of abrasion and the roughness are correlated as long as a similarmanufacturing method and a similar abrasive material are used.

For example, a larger abrasive grain diameter is associated with agreater amount of abrasion and greater roughness. For example, theabrasive force is generally expressed by the roughness as in FIG. 7A inthe case of finishing application, while the abrasive force is generallyexpressed by the amount of abrasion in the case of coarse abrasionapplication. Then, lower limit values and upper limit values of theseare also different. In any case of application, a difference between themaximum abrasive force and the first stage abrasive force widens in thecase of predetermined maximum abrasive force or more, and a multi-stageshape such as the graph G1 clearly appears. That is, a plurality ofstages of abrasive force can be achieved easily with a single wheel.

Durometer hardness of the outer peripheral portion 2B of the abrasiveportion 2 may be 80 or greater, may be 85 or greater, or may be 90 orgreater. Note that a durometer hardness measurement method is based onJIS K 6253 (ISO7619, ASTM D2240). More specifically, the grinding wheel1 of a 50 mm width is placed lying with its radial direction horizontalto the ground, and a durometer GS-719N manufactured by TeclockCorporation was pressed against the outer peripheral portion 2B from thevertical direction (direction orthogonal to the radial direction) withrespect to the ground to perform the measurement. Thus, the maximumabrasive force of the abrasive portion 2 can be increased. When themaximum abrasive force of the abrasive portion 2 is high, the width ofan adjustment margin (plurality of stages) of the abrasive force becomeswider. Hardness of the outer peripheral portion 2B of the abrasiveportion 2 is adjusted by, in addition to hardness of the nonwoven fabricitself, a type and an amount of an adhesive incorporated in the outerperipheral portion 2B and a type and an amount of abrasive grainsincorporated in the outer peripheral portion 2B. In addition, thehardness of the outer peripheral portion 2B is also adjusted by theamount of abrasive grains incorporated in the outer peripheral portion2B. For example, when a comparison is made between the case of using aurethane resin as an adhesive and the case of using a phenol resin as anadhesive, the outer peripheral portion 2B using a phenol resin becomesharder than the outer peripheral portion 2B using a urethane resin. Thatis, the maximum abrasive force is higher in the case of the outerperipheral portion 2B using a phenol resin than the case of the outerperipheral portion 2B using a urethane resin. An upper limit of thedurometer hardness of the outer peripheral portion 2B of the abrasiveportion 2 is not particularly limited (note that the maximum ofdurometer hardness is 100).

Next, a layer configuration of the abrasive portion 2 will be describedwith reference to FIGS. 4A and 4B. As illustrated in FIG. 4A, theabrasive portion 2 is constituted by laminating a plurality of nonwovenfabric sheets 10. The plurality of nonwoven fabric sheets 10 arelaminated with respect to the core member 3 in a direction substantiallyperpendicular to the radial direction (that is, in any of thecircumferential direction and the axial direction). In the presentembodiment, the nonwoven fabric sheets 10 are laminated in thecircumferential direction with respect to the core member 3. Theplurality of nonwoven fabric sheets 10 extend radially outward from theouter circumferential surface of the core member 3 in the radialdirection. The nonwoven fabric sheets 10 adjacent in the circumferentialdirection are disposed in close contact with each other with no gap. Inthis way, the nonwoven fabric sheets 10 that are in close contact witheach other in the circumferential direction are provided throughout theentire circumference in the circumferential direction.

FIG. 4B is a cross-sectional view taken from the direction of an IVbarrow in FIG. 4A. As illustrated in FIG. 4B, each one of the nonwovenfabric sheets 10 extends in the radial direction and in the axialdirection. The inner peripheral portion 2A and the outer peripheralportion 2B are not divided into the nonwoven fabric sheets 10 differentfrom each other, but a region corresponding to the inner peripheralportion 2A and a region corresponding to the outer peripheral portions2B are formed within one nonwoven fabric sheet 10. That is, in theradial direction, the nonwoven fabric 11 constituting the innerperipheral portion 2A and the nonwoven fabric 11 constituting the outerperipheral portion 2B are integrally constituted (diagonal lines in anentirety of FIG. 4B indicate this).

Next, with reference to FIG. 5, a method of manufacturing the grindingwheel 1 according to the present embodiment will be described. FIG. 5 isa conceptual view illustrating a method of manufacturing the grindingwheel 1 according to the present embodiment. As illustrated in theleft-most view in FIG. 5, first, the plurality of nonwoven fabric sheets10 are overlapped to form a preform 17 of the abrasive portion 2. Thepreform 17 is disposed along the outer circumferential surface of thecore member 3. An inner circumferential surface of the preform 17 isbonded to the outer circumferential surface of the core member 3. Then,both end surfaces of the preform 17 are bonded and fixed to each other,and thus the preform 17 constituted in a cylindrical shape is fixed tothe outer circumferential surface of the core member 3 as illustrated inthe second view from the left in FIG. 5. Such a step corresponds to astep of laminating the plurality of nonwoven fabric sheets 10 withrespect to the core member 3 in the circumferential direction.

Next, as illustrated in the third view from the left in FIG. 5, a pasteP including the abrasive grains 12 and an adhesive is attached only to aportion near an outer circumferential surface of the preform 17. Thepaste P is preferably a flowable liquid. Specifically, only the vicinityof the outer circumferential surface of the preform 17 is immersed inthe paste P in a container, and the core member 3 is rotated. Thus, aconfiguration in which the abrasive grains 12 have penetrated thenonwoven fabric over the entire periphery in the vicinity of the outercircumferential surface of the preform 17 is made. However, rather thanthe configuration in which the entire periphery is immersed by rotating,a configuration in which only a portion of the periphery (for example,in stripes or in islands) is immersed may be made.

Here, as illustrated in FIG. 6, the manufacturing method includes thesteps of forming a gap SP between the nonwoven fabric sheets 10 adjacentto each other in the circumferential direction, and incorporatingabrasive grains in an outer peripheral edge portion of each of thenonwoven fabric sheets 10 between which the gap SP is formed.

As illustrated in FIG. 6, specifically, a protrusion 51 is formed in abottom 50 of a container. The outer peripheral edge portion of thenonwoven fabric sheet 10 that is rotating is spaced apart from the othernonwoven fabric sheet 10 adjacent in the circumferential direction byinterference with the protrusion 51. Thus, a gap is formed between thenonwoven fabric sheet 10 interfering with the protrusion 51 and theother nonwoven fabric sheet 10. As the rotation progresses further fromthat state, the nonwoven fabric sheet 10 having interfered with theprotrusion 51 rides over the protrusion 51. Then, the nonwoven fabricsheet 10 having ridden over forms the gap SP with the nonwoven fabricsheet 10 to next interfere with the protrusion 51.

Since the protrusion 51 is formed in the bottom 50 of the container, aplace where the gap SP is formed between the nonwoven fabric sheets 10is filled with the paste P. Accordingly, the paste P together with theabrasive grains penetrates the gap SP between the nonwoven fabric sheets10. Thus, the abrasive grains sufficiently penetrate the outerperipheral edge portion of the nonwoven fabric sheet 10.

Returning to FIG. 5, as illustrated in the fourth view from the left, anexcess of the paste P is removed by rotating the abrasive portion 2after the paste P is applied. As illustrated in the rightmost view ofFIG. 5, the paste P is dried and thus the abrasive portion 2 includesthe outer peripheral portion 2B including the abrasive grains and theinner peripheral portion 2A not including the abrasive grains.

Next, an operation and an effect of the grinding wheel 1 according tothe present embodiment will be described.

The grinding wheel 1 is the grinding wheel 1 including the abrasiveportion 2 including the nonwoven fabric 11, wherein the abrasive portion2 includes the outer peripheral portion 2B formed with the nonwovenfabric 11 including the abrasive grains 12 on the outer peripheral side,and the inner peripheral portion 2A formed with the nonwoven fabric 11not including the abrasive grains 12, and the ratio of the thickness inthe radial direction of the outer peripheral portion to the thickness inthe radial direction of the abrasive portion is from 3% to 60%.

The abrasive portion 2 includes the outer peripheral portion 2B formedwith the nonwoven fabric 11 including the abrasive grains 12 on theouter peripheral side, and the inner peripheral portion 2A formed withthe nonwoven fabric 11 not including the abrasive grains 12. Since theinner peripheral portion 2A is formed with the nonwoven fabric 11 notincluding the abrasive grains 12, the inner peripheral portion 2A issofter than the outer peripheral portion 2B. When the abrasive portion 2is pressed against the object W, the inner peripheral portion 2Adeforms, and thus functions as a cushion against the outer peripheralportion 2B. Therefore, rising of the abrasive force with respect to thepressing amount of the abrasive portion 2 becomes gentle. In this case,the roughness of the surface to be polished of the object W can beadjusted by adjusting the pressing amount of the abrasive portion 2. Inaddition, the ratio of the thickness in the radial direction of theouter peripheral portion to the thickness in the radial direction of theabrasive portion is from 3% to 60%. Since the ratio is 3% or more, it ispossible to suppress the occurrence of early wear, cracking, and thelike of the outer peripheral portion 2B due to the outer peripheralportion 2B being too thin. In addition, the maximum abrasive force ofthe abrasive portion 2 can be increased. Since the ratio is 60% or less,it is possible to suppress difficulty in adjustment of roughness due tothe outer peripheral portion 2B becoming too thick and the abradingportion 2 becoming difficult to deform.

For example, FIG. 7A is a graph illustrating changes in abrasive forceof the grinding wheel 1 according to the embodiment and a grinding wheelaccording to a comparative example. The grinding wheel according to thecomparative example includes an abrasive portion including abrasivegrains in the entire region. That is, the grinding wheel according tothe comparative example does not include a place that functions as acushion, such as the inner peripheral portion 2A of the abrasive portion2 of the present embodiment. The “depth” in the horizontal axisindicates an amount of the depth of pressing (pressing amount), and is avalue indicating how far the abrasive portion 2 is pressed against theobject W. The depth is 0 when the outer peripheral portion 2B of thegrinding wheel 1 touches the object W, and a numerical value increasesas the distance from the center of the grinding wheel 1 to the object Wshortens. The vertical axis indicates the roughness of the surface to bepolished BF of a surface of the object W polished by the abrasiveportion 2, and indicates a value indicating the abrasive force of theabrasive portion 2. The graph G1 shows results obtained when polishingis performed with the grinding wheel 1 according to the embodiment, andthe graph G2 shows results obtained when polishing is performed with thegrinding wheel according to the comparative example.

As shown in the graph G2, the abrasive force of the grinding wheelaccording to the comparative example immediately increases to themaximum abrasive force when the pressing amount is even slightlyincreased. In this case, it is not possible to adjust the abrasive forceby adjusting the pressing amount. On the other hand, as shown in thegraph G1, the abrasive force of the grinding wheel 1 according to theembodiment gradually rises in a state where the pressing amount is low.In the graph G1, as shown by “FG,” a place where the abrasive force doesnot substantially change with respect to the increase in the pressingamount is formed. When the pressing amount is increased further, theabrasive force gradually increases, and when the maximum abrasive forceis reached, the abrasive force becomes substantially constant.

Since the pressing amount and the abrasive force of the grinding wheel 1have relationship such as the graph G1, it is possible to use thegrinding wheel 1 in the following manner. When the object W is polished,first, as illustrated in FIG. 7C, the polishing is performed in a statewhere the pressing amount of the grinding wheel 1 against the object Wis increased. In this case, the polishing (for example, rough finish)can be performed with the grinding wheel 1 in a state where the abrasiveforce is large (see MG in the graph G1 in FIG. 7A). Next, as illustratedin FIG. 7B, the polishing is performed in a state where the pressingamount of the grinding wheel 1 against the object W is reduced, and thusthe polishing (for example, fine finish) can be performed with thegrinding wheel 1 in a state where small abrasive force but fineroughness are obtained (see FG in the graph G1 in FIG. 7A). According tothe use in such a manner, finish polishing can be performed with thegrinding wheel 1 alone, without providing a grinding wheel for roughfinish and a grinding wheel for fine finish.

In addition, the grinding wheel 1 according to the present embodimentincludes less abrasive grains 12 (or no abrasive grains 12) in the innerperipheral portion 2A than in the outer peripheral portion 2B with whichpolishing is performed. Accordingly, since the amount of the abrasivegrains 12 used in the grinding wheel 1 can be suppressed, amanufacturing cost can be suppressed.

In addition, the abrasive portion 2 of the grinding wheel 1 includes theinner peripheral portion 2A that functions as a cushion. Accordingly,the abrasive portion 2 with which polishing is performed can, to someextent, follow a shape of the surface to be polished BF of the object W.

In addition, the grinding wheel 1 according to the present embodiment isthe grinding wheel 1 including the abrasive portion 2 including thenonwoven fabric 11, wherein the abrasive portion 2 includes the outerperipheral portion 2B formed on the outer peripheral side, and the innerperipheral portion 2A softer than the outer peripheral portion 2B, andthe ratio of the thickness in the radial direction of the outerperipheral portion to the thickness in the radial direction of theabrasive portion is from 3% to 60%.

The inner peripheral portion 2A is softer than the outer peripheralportion 2B. When the abrasive portion 2 is pressed against the object W,the inner peripheral portion 2A deforms, and thus functions as a cushionagainst the outer peripheral portion 2B. Thus, it is possible to obtainthe same actions and effects as those described above.

The abrasive portion 2 is constituted by laminating a plurality ofnonwoven fabric sheets, and the plurality of nonwoven fabric sheets arelaminated in a direction substantially perpendicular to the radialdirection. For example, when a long-length nonwoven fabric sheet isspirally wound on a core member, the nonwoven fabric sheet is laminatedin the radial direction. In contrast, in the grinding wheel 1 accordingto the present embodiment, the nonwoven fabric sheets 10 are laminatedin a direction substantially perpendicular to the radial direction.

The nonwoven fabric sheets 10 are laminated in the circumferentialdirection. That is, the nonwoven fabric sheets 10 are provided to beradially formed with respect to the core member 3. In this case, asillustrated in FIGS. 8A to 8E, unlike the case in which the nonwovenfabric sheet 10 is laminated in the axial direction, a trace can beprevented from remaining at a position corresponding to a boundarybetween the nonwoven fabric sheets 10 in the polished surface BF,without moving the grinding wheel 1 in the axial direction whileperforming polishing.

The durometer hardness of the outer peripheral portion 2B is 80 or more.In this case, it is possible to suppress reduction in the maximumabrasive force of the outer peripheral portion 2B.

The nonwoven fabric 11 of the outer peripheral portion 2B includes anyof silicon carbide, diamond, and aluminum oxide as the abrasive grains12. In this case, predetermined abrasive force is obtained.

The method of manufacturing the grinding wheel 1 according to an aspectof the present embodiment is the method of manufacturing the grindingwheel 1 including the core member 3 and the abrasive portion 2 providedaround the outer periphery of the core member 3 and constituted bylaminating the plurality of nonwoven fabric sheets 10, the methodincluding the steps of, laminating the plurality of nonwoven fabricsheets 10 in the circumferential direction, forming a gap between thenonwoven fabric sheets 10 adjacent to each other in the circumferentialdirection, and incorporating the abrasive grains 12 in the outerperipheral edge portion of each of the nonwoven fabric sheets 10 betweenwhich the gap is formed.

The gap is formed between the nonwoven fabric sheets 10 in this way, andthus a state in which the abrasive grains 12 easily penetrate thenonwoven fabric sheets 10 can be achieved. Then, the abrasive grains 12are incorporated in the nonwoven fabric sheets 10 being in a state inwhich the gap is formed, and thus the abrasive grains 12 easilypenetrate the nonwoven fabric sheets 10.

In the embodiment described above, the nonwoven fabric sheets 10 werelaminated in the circumferential direction. Alternatively, the nonwovenfabric sheets 10 may be laminated in the axial direction. For example,as illustrated in FIGS. 8C and 8E, the abrasive portion 2 may be formedby overlapping in the axial direction a plurality of nonwoven fabricsheets 20 each having a disk shape.

In this case, examples of a manufacturing method include a manufacturingmethod illustrated in FIGS. 8A to 8C, and a manufacturing methodillustrated in FIGS. 8D and 8E. In one of the manufacturing methods, asillustrated in FIG. 8A, an abrasive material (including the abrasivegrains 12 and an adhesive) is applied to each nonwoven fabric sheet 20having a disk-shape only at a position corresponding to an outerperipheral portion 20A by spraying or the like. Subsequently, asillustrated in FIG. 8B, an adhesive is applied to an entire surface ofthe nonwoven fabric sheet 20 having a disk shape. Next, as illustratedin FIG. 8C, the plurality of nonwoven fabric sheets 20 to which theadhesive has been applied are laminated in the axial direction. In theother manufacturing method, as illustrated in FIG. 8D, an abrasivematerial (including the abrasive grains 12 and an adhesive) is appliedto each nonwoven fabric sheet 20 having a disk shape only at a positioncorresponding to the outer peripheral portion 20A by spraying or thelike. Subsequently, as illustrated in FIG. 8E, the plurality of nonwovenfabric sheets 20 are laminated in the axial direction and held by aholder 25 from both sides in the axial direction.

Second Embodiment

Next, a grinding wheel 100 according to a second embodiment will bedescribed with reference to FIG. 10. According to this grinding wheel100, while an amount of abrasive grains is suppressed to suppress amanufacturing cost, adjustment of abrasive performance according to aneed is facilitated, and at the same time abrasive performance can bestabilized even when polishing progresses and an outer peripheralportion 2B is shaved.

Specifically, in addition to an inner peripheral portion 2A and theouter peripheral portion 2B, an abrasive portion 2 of the grinding wheel100 includes an intermediate portion 2C between the outer peripheralportion 2B and the inner peripheral portion 2A, as a layer differentfrom the outer peripheral portion 2B and the inner peripheral portion2A.

The thickness in the radial direction of the abrasive portion 2 isreferred to as a “thickness R1,” and the thickness in the radialdirection of the intermediate portion 2C is referred to as a “thicknessR3.” At this time, a ratio of a sum of the thickness R3 of theintermediate portion 2C and the thickness R2 of the outer peripheralportion 2B to the thickness R1 of the abrasive portion 2(=(R3+R2)×100/R1) may be set to 3% or more, may preferably be set to 5%or more, and may be set to 10% or more.

The intermediate portion 2C includes at least a resin material. Asimilar material to the materials exemplified for the above-describedadhesive 13 can be used as the resin material. The outer peripheralportion 2B and the intermediate portion 2C may include the same resinmaterial. Alternatively, the outer peripheral portion 2B and theintermediate portion 2C may include different resin materials.

Hardness of the intermediate portion 2C will be described. The hardnessof the intermediate portion 2C may be set appropriately according toabrasive performance required of the grinding wheel 100, and the like.The intermediate portion 2C may be harder than the inner peripheralportion 2A. Durometer hardness of the intermediate portion 2C may be,for example, +1 or more, may be +3 or more, or may be +5 or more ascompared to the inner peripheral portion 2A. In this case, theintermediate portion 2C can support the outer peripheral portion 2B morefirmly than the inner peripheral portion 2A. For example, a state suchas hardness of the outer peripheral portion 2B changes between the startof polishing and after polishing for a long period of time. Theintermediate portion 2C supports the outer peripheral portion 2B morefirmly than the inner peripheral portion 2A, and thus can reduce theinfluence of the change in the outer peripheral portion 2B. Thus, theabrasive performance of the grinding wheel 100 can be stabilized.

The intermediate portion 2C may be harder than, softer than, or as hardas the outer peripheral portion 2B. However, when the intermediateportion 2C is harder than the outer peripheral portion 2B, theintermediate portion 2C that is hard can support the outer peripheralportion 2B from underneath to suppress deformation of the outerperipheral portion 2B that is soft and that attempts to deform towardthe inner peripheral side more than necessary at the time of polishing.Note that in a case where the intermediate portion 2C is made harderthan the outer peripheral portion 2B, the durometer hardness of theintermediate portion 2C may be, for example, +1 or more, may be +3 orgreater, or may be +5 or greater, as compared to the outer peripheralportion 2B.

When the outer peripheral portion 2B includes a lubricant, the effect ofthe intermediate portion 2C supporting the outer peripheral portion 2Bfrom underneath becomes more significant. The lubricant may be of powderor may be of liquid. The lubricant functions as a material forsuppressing a “smear” (smearing inhibitor) during polishing. Generallyundesirable smearing may occur when a workpiece that is in contact withthe resin material of the outer peripheral portion 2B becomessufficiently hot, and some of the resin material of the outer peripheralportion 2B softens and moves to the workpiece. When the lubricant isincorporated in the outer peripheral portion 2B in this manner, althoughsmearing can be suppressed, the outer peripheral portion 2B becomessoft. In this case, the intermediate portion 2C that is hard cansuppress deformation of the outer peripheral portion 2B that becomessoft due to the influence of the lubricant and that attempts to deformtoward the inner peripheral side more than necessary during polishing.

Examples of the lubricant include a metal salt of a fatty acid (forexample, lithium stearate, zinc stearate), a solid lubricant (forexample, (poly) tetrafluoroethylene (PTFE), graphite and molybdenumdisulfide), mineral oil and wax, carboxylic acid ester (for example,butyl stearate), poly (dimethylsiloxane) gum, and a combination thereof.Such lubricants and sources of such commercially available lubricantsare known in the art.

A method of manufacturing the grinding wheel 100 according to the secondembodiment will be described. First, as illustrated in FIG. 5, a casewhere a paste P is attached in the vicinity of an outer circumferentialsurface of a preform 17 will be described. In this case, first, thepaste P associated with the resin material for forming the intermediateportion 2C is attached to the preform 17. Subsequently, the paste Passociated with the resin material for forming the outer peripheralportion 2B is attached to the preform 17. In the second attachment step,the paste P is prevented from being attached to a portion correspondingto the intermediate portion 2C, and the paste P is attached only to aportion corresponding to the outer peripheral portion 2B.

The method illustrated in FIGS. 8A to 8E may also be used formanufacturing the grinding wheel 100 according to the second embodiment.In this case, the resin material for the outer peripheral portion 2B isapplied to the portion corresponding to the outer peripheral portion 2B,and the resin material for the intermediate portion 2C is applied to theportion corresponding to the intermediate portion 2C.

As described above, in the grinding wheel 100 according to the secondembodiment, the abrasive portion 2 includes the outer peripheral portion2B formed on the outer peripheral side, the inner peripheral portion 2Asofter than the outer peripheral portion 2B, and the intermediateportion 2C disposed between the outer peripheral portion 2B and theinner peripheral portion 2A, the intermediate portion 2C being a layerdifferent from the outer peripheral portion 2B and the inner peripheralportion 2A, and including at least the resin material.

When the abrasive portion 2 includes only the inner peripheral portion2A and the outer peripheral portion 2B, parameters that can be adjustedaccording to required abrasive performance are only sizes and materialsof the two layers, but when the abrasive portion 2 includes theintermediate portion 2C, a size and a material of the intermediateportion 2C can also be adjusted. Accordingly, adjustment of the grindingwheel 100 according to required abrasive performance is facilitated.Note that since the grinding wheel 100 can correspond to various needs,for example, when polishing at two stages such as rough finish and finefinish as in the case of the first embodiment is not required, there maybe a case where the abrasive performance as illustrated by the graph G2in FIG. 7A is required. The grinding wheel 100 according to the secondembodiment can correspond to the abrasive performance required in suchpolishing at one stage.

In addition, the grinding wheel 100 according to the second embodimentalso includes less abrasive grains 12 (or no abrasive grains 12) in theinner peripheral portion 2A than in the outer peripheral portion 2B withwhich polishing is performed. Accordingly, since an amount of theabrasive grains 12 used in the grinding wheel 100 can be suppressed, amanufacturing cost can be suppressed.

The intermediate portion 2C may be harder than the inner peripheralportion 2A. In this case, even when the hardness of the outer peripheralportion 2B changes between the start of polishing and after the progressof the polishing, abrasive performance can be stabilized by theintermediate portion 2C supporting the outer peripheral portion 2B.

The intermediate portion 2C may be harder than the outer peripheralportion 2B. In this case, even when the outer peripheral portion 2B issoft, the outer peripheral portion 2B can be supported from underneathand it is possible to suppress the outer peripheral portion 2B deformingtoo far toward the inner peripheral side.

The outer peripheral portion 2B may include the lubricant. The lubricantfunctions, for example, as a smearing inhibitor. In addition, althoughthe outer peripheral portion 2B easily becomes soft when the lubricantis included, the intermediate portion 2C supports the outer peripheralportion 2B from underneath, and thus high abrasive performance can beexhibited while smearing is suppressed.

The outer peripheral portion 2B and the intermediate portion 2C mayinclude the same resin material. In this case, manufacturing is madeeasy. In addition, since there is no mixing of different resins when theouter peripheral portion 2B and the intermediate portion 2C are formed,product stability is improved.

EXAMPLES

Next, examples will be described, but the grinding wheel according tothe present disclosure is not limited to the following grinding wheels.

Grinding wheels according to Examples 1 to 4 and a grinding wheelaccording to a comparative example were prepared. In the grinding wheelof each of Example 1 to 4 and the comparative example, an overall radiuswas 152.5 mm, the thickness in the radial direction of the entireabrasive portion was 84 mm, and a dimension in the axial direction(width of the grinding wheel) was 50 mm. Then, an outer peripheralportion of the grinding wheel of Example 1 had a thickness in the radialdirection of 5 mm (ratio is 5.9%). An outer peripheral portion of thegrinding wheel of Example 2 had a thickness in the radial direction of10 mm (ratio is 11.9%). An outer peripheral portion of the grindingwheel of Example 3 had a thickness in the radial direction of 20 mm(ratio is 23.8%). An outer peripheral portion of the grinding wheel ofExample 4 had a thickness in the radial direction of 30 mm (ratio is35.7%). The grinding wheel of the comparative example had no outerperipheral portion and no inner peripheral portion, and an abrasiveportion entirely included abrasive grains (ratio is 100%).

Other conditions for the grinding wheels of Examples 1 to 4 and thecomparative example were as follows. That is, an adhesive for holdingabrasive grains was an adhesive based on a phenol resin. A material ofthe abrasive grains was silicon carbide. Nonwoven fabric sheets werelaminated in the circumferential direction. The outer peripheral portionincluded the abrasive grains by an amount of 162 gram. The innerperipheral portion included no abrasive grains in nonwoven fabric. Asregards durometer hardness of the outer peripheral portions of suchgrinding wheels, the durometer hardness was 93.2 for the comparativeexample, 90.4 for Example 1, 92.1 for Example 2, 92.6 for Example 3, and93 for Example 4. In addition, an object made of a material such as JISG 3141 compliant SPCC-SB (cold-rolled steel plate, standard hardness,and bright finish) was polished while the depth was changed. Conditionsof a planar abrader were as follows: “wheel rotation speed: 2000 rpm,test work feed speed: 1 MPM, lubricant: water.” Roughness of a polishedsurface of the object was measured. Measurement results are shown inFIG. 9.

In an experiment of FIG. 9, to confirm the effect specific to thegrinding wheel according to the first embodiment, observation was madein a viewpoint of whether a plurality of stages of abrasive force can beapplied stably to the surface to be polished of the object. Here,although the grinding wheel according to the second embodiment includesa grinding wheel that exhibits a curve close to that of “ComparativeExample” in FIG. 9 in the experiment of FIG. 9, the effect of the secondembodiment is not denied, and the second embodiment is not excluded fromthe scope of the present invention.

1. A grinding wheel comprising an abrasive portion including nonwoven fabric, wherein the abrasive portion includes an outer peripheral portion formed with the nonwoven fabric including abrasive grains on an outer peripheral side, and an inner peripheral portion formed with the nonwoven fabric not including the abrasive grains, and a ratio of a thickness in a radial direction of the outer peripheral portion to a thickness in a radial direction of the abrasive portion is from 3% to 60%.
 2. A grinding wheel comprising an abrasive portion including nonwoven fabric, wherein the abrasive portion includes an outer peripheral portion formed on an outer peripheral side, and an inner peripheral portion softer than the outer peripheral portion, and a ratio of a thickness in a radial direction of the outer peripheral portion to a thickness in a radial direction of the abrasive portion is from 3% to 60%.
 3. The grinding wheel according to claim 1, wherein the abrasive portion is constituted by laminating a plurality of nonwoven fabric sheets, and the plurality of nonwoven fabric sheets are laminated in a direction substantially perpendicular to the radial direction.
 4. The grinding wheel according to claim 3, wherein the nonwoven fabric sheets are laminated in a circumferential direction.
 5. The grinding wheel of claim 3, wherein the nonwoven fabric sheets are laminated in an axial direction.
 6. The grinding wheel according to claim 1, wherein durometer hardness of the outer peripheral portion is 80 or greater.
 7. (canceled)
 8. The grinding wheel according to claim 1, wherein the abrasive portion comprises: an outer peripheral portion formed on an outer peripheral side; an inner peripheral portion softer than the outer peripheral portion; and an intermediate portion disposed between the outer peripheral portion and the inner peripheral portion, the intermediate portion being a layer different from the outer peripheral portion and the inner peripheral portion, and including at least a resin material.
 9. The grinding wheel according to claim 8, wherein the intermediate portion is harder than the inner peripheral portion.
 10. The grinding wheel according to claim 8, wherein the intermediate portion is harder than the outer peripheral portion.
 11. The grinding wheel according to claim 8, wherein the outer peripheral portion includes a lubricant.
 12. The grinding wheel according to claim 8, wherein the outer peripheral portion and the intermediate portion include the same resin material.
 13. A method of manufacturing a grinding wheel comprising an abrasive portion constituted by laminating a plurality of nonwoven fabric sheets, the method comprising the steps of: laminating a plurality of nonwoven fabric sheets in a circumferential direction; forming a gap between the nonwoven fabric sheets adjacent to each other in the circumferential direction; and incorporating abrasive grains in an outer peripheral edge portion of each of the nonwoven fabric sheets between which the gap is formed.
 14. The grinding wheel according to claim 2, wherein the abrasive portion is constituted by laminating a plurality of nonwoven fabric sheets, and the plurality of nonwoven fabric sheets are laminated in a direction substantially perpendicular to the radial direction.
 15. The grinding wheel according to claim 14, wherein the nonwoven fabric sheets are laminated in a circumferential direction.
 16. The grinding wheel of claim 14, wherein the nonwoven fabric sheets are laminated in an axial direction.
 17. The grinding wheel according to claim 2, wherein durometer hardness of the outer peripheral portion is 80 or greater.
 18. The grinding wheel according to claim 2, wherein the abrasive portion comprises: an outer peripheral portion formed on an outer peripheral side; an inner peripheral portion softer than the outer peripheral portion; and an intermediate portion disposed between the outer peripheral portion and the inner peripheral portion, the intermediate portion being a layer different from the outer peripheral portion and the inner peripheral portion, and including at least a resin material.
 19. The grinding wheel according to claim 18, wherein the intermediate portion is harder than the inner peripheral portion.
 20. The grinding wheel according to claim 18, wherein the intermediate portion is harder than the outer peripheral portion.
 21. The grinding wheel according to claim 18, wherein the outer peripheral portion includes a lubricant. 